A conventional thrust vectoring and thrust reversing variable-area exhaust nozzle is known in accord with the teaching of U.S. Pat. No. 4,175,385, of D. O. Nash, and assigned to the General Electric Company. This nozzle achieves variable-area by a combination of plural flap members moving in coordination between spaced apart vertical side walls. At least four flap members are used, and their movement between the spaced apart vertical side walls requires coordination of several actuators. Similarly, this nozzle provides thrust vectoring and thrust reversing by the movement of a cowl member about first and second spaced apart axes transverse to the axis of the exhaust nozzle. The cowl member carries a separate movable lip member which is pivotal relative thereto as the cowl member pivots about the first and second axes relative to the remainder of the exhaust nozzle. A brief perusal of the '385 patent will quickly reveal that a large number of actuators is required to utilize this nozzle. Additionally these actuators must be operated in a coordinated fashion in order to achieve the objectives of the invention. In addition, this nozzle employs a separate arcuate deflector member which is movable arcuately from a position outside of the fluid flow stream to a position within the stream for achieving thrust vectoring of the type required for short or vertical take off and landing of an aircraft (i.e., STOL or VTOL). This deflector requires still more actuators for its operation.
Overall, the teaching of the '385 patent must be considered as complex and as requiring a multitude of component parts. Further, the nozzle requires coordination of multiple actuators to achieve its goals. Finally, the '385 teaching does not address the problem of achieving motive gas sealing between the multitude of relatively moving parts of the nozzle. Without adequate sealing between the parts of a variable exhaust nozzle, leakage of motive gas will compromise the performance of the nozzle, and of the aircraft upon which the nozzle is installed.
A more recent thrust vectoring exhaust nozzle for aircraft is known in accord with the teaching of U.S. Pat. No. 4,660,767, of H. A. Scarce, and assigned to Rolls-Royce. This later effort is notable for its simplicity in comparison with the earlier '385 patent. Particularly the '767 patent utilizes a relatively simple cowl member which is pivotally movable between a first position removed from the fluid flow stream and a second position in which the cowl member deflects the fluid stream. A flap is coordinated with the movement of the cowl member by simple linkage such that the flap member moves from a position bounding the lower floor of the fluid flow path to a position providing guidance to the deflected flow stream as the latter is directed downwardly and perhaps also slightly forwardly by the cowl member. This nozzle is intended primarily for use on a vertical take off and landing (VTOL) aircraft, and as such is not intended to accomplish variable-area or thrust reversing as is required for high performance jet aircraft to enhance flight maneuverability and shorten landing roll.
It will be seen from the above that while the nozzle apparatus according to the '767 patent provides a reduced parts count and simplicity of operation and structure in comparison with the '385 patent, the former nozzle does not provide either variable-area or thrust reversing capability as does the latter teaching. Therefore, it is apparent that a need exists in the pertinent art for an exhaust nozzle which will provide all three functions of variable-area, thrust vectoring, and thrust reversing, while also providing relatively simple structure and ease of operation with a minimal number of actuators. The structure of such an exhaust nozzle should also be relatively light so that the increased performance offered by such a nozzle is not substantially canceled by the weight penalty of the nozzle itself. Further, such an exhaust nozzle should not significantly increase the envelope of the vehicle upon which it is installed. That is, the exhaust nozzle in its basic structure and actuators required for its operation should not present drag-producing structures which extend into the airstream around the vehicle or require undesirably bulky nacelles or other aerodynamic fairings to shield such parts of the nozzle.